Serialize nested models as a keyed JSON object in Django

Question

I have a Django model that has many=True nesting, and I'd like to serializer the nested objects (in Django Rest Framework) as an object instead of a list (which is the default in DRF).

Adding many=True serializes things as a list.

class PostSerializer(serializers.ModelSerializer):
  votes = VoteSerializer(many=True)

Instead of rendering the votes as a list of objects:

[... posts: [{id: 123, user: A}, {id: 456, user: B}, ....]

I'd like to render votes as a list of objects keyed by id:

[... posts: {123: {user: A}, 456: {user: B}}, ...]

Daniel Roseman · Accepted Answer · 2019-08-02 18:33:36Z

1

This is poking into a private API and isn't exactly concise, but should work.

class DictManyRelatedField(serializers.ManyRelatedField):
    def to_representation(self, iterable):
        return {
           value.pk: self.child_relation.to_representation(value)
           for value in iterable
        }


class VoteSerializer(serializers.ModelSerializer):
    user = serializers.CharField()

    class Meta:
        model = Vote
        fields = ('user',)

    @classmethod
    def many_init(cls, *args, **kwargs):
        kwargs['child_relation'] = cls()
        return DictManyRelatedField(*args, **kwargs)


class PostSerializer(serializers.ModelSerializer):
    votes = VoteSerializer(read_only=True, many=True)

    class Meta:
        model = Post
        fields = ('votes',)

answered Aug 2, 2019 at 18:33

Daniel Roseman

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